THE CLUSTER OF GALAXIES SURROUNDING CYGNUS-A

We report optical imaging and spectroscopy of 41 galaxies in a 22' squ are region surrounding Cygnus A, The results show that there is an ext ensive rich cluster associated with Cyg A of Abell richness of at leas t I and possibly as high as 4. The velocity histogram has two peaks, o ne centered on Cyg A and a more significant peak redshifted by about 2 060 km s(-1) from the velocity of Cyg A. The dynamical centroid of the spatial distribution is also shifted somewhat to the northwest, Howev er, statistical tests show only weak evidence that there are two disti nct clusters, The entire system has a velocity dispersion of 1581 km s (-1), which is slightly larger than other, well-studied examples of ri ch clusters.